1. Field of the Invention
The present invention relates to a mobile object search system which performs a continuous search of a mobile service network to ascertain the location of mobile objects, and to a mobile object search method.
2. Related Arts
When a search of a mobile service network is performed for a mobile object which has issued a malicious call, because such an object is not established at a permanent location and can be moved from place to place, it is important that the latest known location of the mobile object be immediately available.
According to the prior art, information concerning the location of a mobile object is output each time the object""s location is registered at a mobile object switchboard, i.e., a mobile service switching center (MSC) provided for a mobile service network.
Therefore, since the frequent registration of locations imposes a heavy load on a mobile service network, the geographical range of a location registration area is quite large. And in Japan, an example location registration area is equivalent in size to that of a prefecture.
Thus, as it is not possible to designate a smaller search area, a large location registration area must be specified when attempting to locate a mobile object which issued a call. This constitutes an especially grave impediment when there is a socially important reason for a search, such as when a mobile object must be located from which a call was issued which is associated with a crime.
Since the prior art employs the location registration area when referring to a mobile object from which a malicious call has been issued, when searching for the location of a mobile object it is difficult to designate a deployment range smaller than the location registration area. It is, therefore, one objective of the present invention to provide a mobile object search system by which the location of a mobile object can be specified which lies within a radio zone range to which the range of only one base station corresponds, and a mobile object search method therefor.
To achieve the above objective, according to one aspect of the present invention, a mobile object search system includes:
a database for which is provided a mobile object tracing indication to enable the continuous monitoring of the location of a mobile object which has issued a call when a request for location information concerning the mobile object is transmitted to a switchboard in a mobile service system;
mobile object tracing means for registering a mobile object display in the data base; and
mobile object location monitoring means for repeatedly monitoring the location of the mobile object, and for using a notification of a change in the location of the mobile object by a minimum control area unit which the mobile object communication network recognizes.
The minimum control area unit is a radio zone for one base station.
According to another aspect of the present invention, the mobile object tracing means and the mobile object location monitoring means are included in a location register, and the mobile object tracing means includes mobile object tracing start means for initiating a mobile object tracing process, and a mobile object tracing halting means for halting the tracing of the mobile object.
According to an additional aspect, location registration means for storing the location information is included in the location register. The mobile object location monitoring means includes a function for issuing notifications that location registrations have been performed, and continuously issues notifications of location changes in accordance with the location registrations by the minimum control area unit of the location registration area.
According to either aspect, when the mobile object moves to a location registration area of another network, the mobile object tracing display is transmitted so as to operate the mobile object location monitoring means of the network wherein the mobile object is located.
In addition, to achieve the above objective, according to a further aspect of the present invention a mobile object search method comprises the steps of:
transmitting, to a mobile service switching center in a mobile service system, a request for location information concerning a mobile object from which a call has been issued;
setting, in a database for the mobile service switching center, a mobile object tracing display in order to perform the continuous monitoring of the location of the mobile object; and
transmitting notifications of a change in the location of the mobile object by a minimum control area unit which the mobile service network recognizes.
According to still another aspect, the minimum control area unit constitutes a radio zone for one base station.
According to a still additional aspect, the mobile object search method further comprises the steps of:
updating the database, based on the request for a search for the location information concerning the mobile object from which a call has been issued, by setting a mobile service switching center number in a location registration area wherein the mobile object is located and by establishing a fact that a radio zone is unknown;
forwarding a request for a mobile object location examination to a mobile service switching center which corresponds to the mobile service switching center number;
specifying, by paging, a radio zone in which the mobile object is located when a response is received to the request for the mobile object location examination;
outputting the specified radio zone as location information; and
updating the database by setting the specified radio zone in the database.
According to a still further objective, the mobile object search method further comprises the steps of:
starting a timer after the location information is updated; and
issuing another request for a search for location information concerning the mobile object when the timer count equals a predetermined value.
In addition, the mobile object is controlled by the mobile service switching center so that power is at least supplied to a wireless circuit in the mobile object. Specifically, in response to a power-OFF operation for the mobile object, only the supply of power to the interface of the mobile object would be halted. Thus, there is no chance that the search for the mobile object will be disabled when the mobile object is powered off.
Furthermore, a radio zone in which the mobile object, which is a target of the tracing display is present is periodically monitored, and changes in the location of the mobile object are sequentially reported to the mobile service switching center.
Further, a change in the movement of the mobile object in the radio zone is periodically monitored, and when the radio zone is changed, that effect is reported to the mobile service switching center.
Moreover, a radio zone in which the mobile object is currently present is compared with a radio zone in which the mobile object was previously present, and when a plurality of matches are detected, a change in the radio zone is reported to the mobile service switching center. As a result, it is possible to avoid frequent notifications of changes in the radio zone of the mobile object.
Other objectives and features of the present invention will become apparent during the course of the description of the embodiments which is given while referring to the accompanying drawings.